XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3501
a higher conversion was obtained (Park &Fan, 2004). Both
hydrochloric acid (HCl) and nitric acid (HNO3) were
found to be effective in releasing multivalent ions from
serpentine minerals for carbonation reactions. At 4M con-
centration, HCl and HNO3 extracted majority of divalent
ions from serpentine minerals followed by carbonation at
pH of 9, forming hydromagnesite (Teir et al., 2007). Sun
et al. used NH4HCl solution to extract divalent ions from
steelmaking slags (Sun et al., 2011). Galina et al. explored
enhancements in CO2 capture via pH-swing mineral car-
bonation, focusing on refining the process parameters for
acid dissolution of serpentine. Their experiments, con-
ducted under stoichiometric and atmospheric conditions
using hydrochloric acid, achieved an impressive 96% effi-
ciency in extracting magnesium at 100°C with 2.5 M HCl.
The method was further refined by using NaOH to precipi-
tate Fe3+ at a pH of 5, followed by Fe2+ at pH 9, and per-
forming carbonation at a higher pH of 11. This approach
yielded a 90% conversion rate under a CO2 pressure of 150
bar. The research findings suggest that the reaction duration
can be effectively shortened to 30 minutes, still achieving
over 90% efficiency in magnesium extraction (Galina et al.,
2023).
Direct mineral carbonation utilizes sodium bicar-
bonate (NaHCO3) to achieve carbonate conversions
(O’Connor et al., 2001 Wang et al., 2019). The effect of
various factors on the dissolution rate of olivine and over-
all carbonation rate during mineral carbonation has been
studied. The study revealed that various organic acids and
ligands, including EDTA and potassium hydrogen phthal-
ate, enhance the metal dissolution rate from hosting min-
erals (Crundwell, 2014). In addition to enhancing the
metal dissolution efficiency of olivine minerals, acids have
been utilized to recover valuable minerals such as nickel,
magnesium, and iron from the olivine structure. Matus et
al. proposed a new mechanism for metal extraction from
olivine-bearing ore by avoiding silica gel formation dur-
ing leaching with hydr°Chloric acid and including a car-
bonation pre-treatment. It was found that pre-treatment
significantly improved the leaching efficiency, achieving
more than 60% efficiency compared to about 35% without
pre-treatment (Matus et al., 2020). Wang et al utilized a
mixed gas of 95% CO2 and 5% H2S and sodium sulfide
to extract nickel from olivine during carbonation reactions.
Results indicated nickel conversion efficiency in about 63%
to 80% (F. Wang et al., 2021). Sodium chloride (NaCl) has
been shown to improve the extent of mineral carbonation.
Gadikota et al. showed that increasing the concentration of
NaCl to 1M increased carbonate yield. However, the effect
of the electrolyte is not significant when no buffer is present
(Gadikota et al., 2014). O’Connor et al. suggested that the
improvement in the reaction rate by the addition of NaCl
is as a result Cl- ions which may help activate the mineral
(O’Connor et al., 2000). At pressures of 15MPa and 185°C
the addition of 1M NaCl and 0.64M NaHCO3 improved
the carbonation conversion to 34% after 1 hour of reac-
tion (Chizmeshya et al., 2007). The authors attribute the
higher carbonation conversation rate to the presence of Na+
ions that may modify the surface charge of silicate particles
aiding ion exchange at the solid/liquid interphase and the
presence of Cl– ions increase the solubility of divalent ions
in the solutions (O’Connor et al., 2005). Irrespective of the
impact on mineral carbonation efficiency, the addition of
sodium chloride salts have some effects on the sequestration
reactions (Grant &Harlov, 2018 Prigiobbe et al., 2009).
King et al. studied magnesite precipitation in saline solu-
tions in unstirred batch reactors to provide insight into the
formation of secondary reaction products during olivine
carbonation reactions. It was observed that at a temperature
of 160°C, the morphology of carbonate crystals changed
from the standard rhombohedral structure to a layered
structure. The morphology of carbonate product was more
developed in reactions with increasing ionic strengths (King
et al., 2010). Turri et al explored two methodologies for
olivine carbonation: direct and indirect. While the direct
process is simpler, its efficiency was limited by passivation
layer formation. Conversely, the indirect process, though
more intricate, resulted in superior dissolution yields and
high product separation efficiencies (Turri et al., 2019).
Sodium chloride (NaCl) was the only electrolyte that
has been extensively studied, and no other inorganic elec-
trolyte has been studied yet. The knowledge gap was how
different inorganic salts might impact (enhance or prevent)
mineral carbonation reactions. In this study, the effect of
Na2SO4 and various other inorganic electrolytes on the
kinetics of mineral carbonation for olivine minerals was
investigated. The carbonation ratio of olivine minerals was
determined using thermogravimetric analysis (TGA). The
particle size distribution, mineralogy, and bulk morphol-
ogy of carbonated products were examined using particle
size analyzer, XRD and SEM. In addition, the mechanism
of mineral carbonation for olivine minerals was examined
using E-SEM.
MATERIALS AND METHODS
Materials
Olivine rock sample was obtained from Ward’s Science.
The olivine sample was crushed and ground to obtain
fractions of below 600 mm. The feed material was further
downsized in wet using an attrition mill with steel balls as
a higher conversion was obtained (Park &Fan, 2004). Both
hydrochloric acid (HCl) and nitric acid (HNO3) were
found to be effective in releasing multivalent ions from
serpentine minerals for carbonation reactions. At 4M con-
centration, HCl and HNO3 extracted majority of divalent
ions from serpentine minerals followed by carbonation at
pH of 9, forming hydromagnesite (Teir et al., 2007). Sun
et al. used NH4HCl solution to extract divalent ions from
steelmaking slags (Sun et al., 2011). Galina et al. explored
enhancements in CO2 capture via pH-swing mineral car-
bonation, focusing on refining the process parameters for
acid dissolution of serpentine. Their experiments, con-
ducted under stoichiometric and atmospheric conditions
using hydrochloric acid, achieved an impressive 96% effi-
ciency in extracting magnesium at 100°C with 2.5 M HCl.
The method was further refined by using NaOH to precipi-
tate Fe3+ at a pH of 5, followed by Fe2+ at pH 9, and per-
forming carbonation at a higher pH of 11. This approach
yielded a 90% conversion rate under a CO2 pressure of 150
bar. The research findings suggest that the reaction duration
can be effectively shortened to 30 minutes, still achieving
over 90% efficiency in magnesium extraction (Galina et al.,
2023).
Direct mineral carbonation utilizes sodium bicar-
bonate (NaHCO3) to achieve carbonate conversions
(O’Connor et al., 2001 Wang et al., 2019). The effect of
various factors on the dissolution rate of olivine and over-
all carbonation rate during mineral carbonation has been
studied. The study revealed that various organic acids and
ligands, including EDTA and potassium hydrogen phthal-
ate, enhance the metal dissolution rate from hosting min-
erals (Crundwell, 2014). In addition to enhancing the
metal dissolution efficiency of olivine minerals, acids have
been utilized to recover valuable minerals such as nickel,
magnesium, and iron from the olivine structure. Matus et
al. proposed a new mechanism for metal extraction from
olivine-bearing ore by avoiding silica gel formation dur-
ing leaching with hydr°Chloric acid and including a car-
bonation pre-treatment. It was found that pre-treatment
significantly improved the leaching efficiency, achieving
more than 60% efficiency compared to about 35% without
pre-treatment (Matus et al., 2020). Wang et al utilized a
mixed gas of 95% CO2 and 5% H2S and sodium sulfide
to extract nickel from olivine during carbonation reactions.
Results indicated nickel conversion efficiency in about 63%
to 80% (F. Wang et al., 2021). Sodium chloride (NaCl) has
been shown to improve the extent of mineral carbonation.
Gadikota et al. showed that increasing the concentration of
NaCl to 1M increased carbonate yield. However, the effect
of the electrolyte is not significant when no buffer is present
(Gadikota et al., 2014). O’Connor et al. suggested that the
improvement in the reaction rate by the addition of NaCl
is as a result Cl- ions which may help activate the mineral
(O’Connor et al., 2000). At pressures of 15MPa and 185°C
the addition of 1M NaCl and 0.64M NaHCO3 improved
the carbonation conversion to 34% after 1 hour of reac-
tion (Chizmeshya et al., 2007). The authors attribute the
higher carbonation conversation rate to the presence of Na+
ions that may modify the surface charge of silicate particles
aiding ion exchange at the solid/liquid interphase and the
presence of Cl– ions increase the solubility of divalent ions
in the solutions (O’Connor et al., 2005). Irrespective of the
impact on mineral carbonation efficiency, the addition of
sodium chloride salts have some effects on the sequestration
reactions (Grant &Harlov, 2018 Prigiobbe et al., 2009).
King et al. studied magnesite precipitation in saline solu-
tions in unstirred batch reactors to provide insight into the
formation of secondary reaction products during olivine
carbonation reactions. It was observed that at a temperature
of 160°C, the morphology of carbonate crystals changed
from the standard rhombohedral structure to a layered
structure. The morphology of carbonate product was more
developed in reactions with increasing ionic strengths (King
et al., 2010). Turri et al explored two methodologies for
olivine carbonation: direct and indirect. While the direct
process is simpler, its efficiency was limited by passivation
layer formation. Conversely, the indirect process, though
more intricate, resulted in superior dissolution yields and
high product separation efficiencies (Turri et al., 2019).
Sodium chloride (NaCl) was the only electrolyte that
has been extensively studied, and no other inorganic elec-
trolyte has been studied yet. The knowledge gap was how
different inorganic salts might impact (enhance or prevent)
mineral carbonation reactions. In this study, the effect of
Na2SO4 and various other inorganic electrolytes on the
kinetics of mineral carbonation for olivine minerals was
investigated. The carbonation ratio of olivine minerals was
determined using thermogravimetric analysis (TGA). The
particle size distribution, mineralogy, and bulk morphol-
ogy of carbonated products were examined using particle
size analyzer, XRD and SEM. In addition, the mechanism
of mineral carbonation for olivine minerals was examined
using E-SEM.
MATERIALS AND METHODS
Materials
Olivine rock sample was obtained from Ward’s Science.
The olivine sample was crushed and ground to obtain
fractions of below 600 mm. The feed material was further
downsized in wet using an attrition mill with steel balls as